1. Field of the Invention
The present invention relates to graph displaying devices and methods which input functional expression data to display same as a graph and more particularly to a graph display device and method which displays input functional expression data graph in color on a color display device.
2. Description of the Related Art
Conventionally, a graph display device, for example, for an electronic graphic calculator which displays input functional expression data as a graph, has been put to practical use.
In the graph display device of this type, when functional data, for example for Y=f(X), is input, numerical values obtained depending on range data set in a range of display on the display device are input to the functional expression and operated to produce graph delineating data which is then displayed as a graph. In this case, with a conventional graph display device and, more particularly, with an electronic graphic calculator, the input functional expression data and its graph data are displayed in black on a white screen of a liquid crystal display device.
When, for example, an X-coordinate range is set to display a graph for functional expression data, only graph data in the set range is displayed as a graph irrespective of the maximum coordinate range displayable in the whole display area of the liquid crystal display.
When only graph data in a set range of coordinates is displayed as a graph as in the conventional graph display device, however, the whole shape of the graph is difficult to understand. Thus, it is necessary to additionally display graph data outside the set range in some form separately from the graph data in the set range.
Graph data for the input functional expression data is conventionally all displayed usually in the same color, so that when, for example, plural-functional expression data is input and the corresponding individual-graph data are together displayed, the individual-graph data are very difficult to discriminate from each other.